//private function to recursively free the subtree rooted at node
static void treeNode_free(treeNode* node) {
// printf("about to try to free a node! \n");
if(!node) return;
if(node->left) treeNode_free(node->left);
if(node->right) treeNode_free(node->right);
free(node);
}
/* free all memory allocated for the tree, including the tree
itself */
void kdtree_free(kdtree *tree) {
if (!tree) return;
treeNode_free(tree->root);
free(tree);
}